NEW ORLEANS -- A Super Bowl week that had gone so smoothly for the Big Easy suddenly turned bizarre when everyone was watching.

The lights went out on the biggest game of the year.

Just imagine the uproar if Baltimore had lost.

The outage, blamed on an unspecified "abnormality" in the Superdome's power system, was an embarrassment for New Orleans, which was hosting its first Super Bowl since 2002 and was eager to show off how it has been rebuilt since Hurricane Katrina.

Mayor Mitch Landrieu called Sunday night's outage "an unfortunate moment in what has been an otherwise shining Super Bowl week for the city of New Orleans."

He said he expected to receive "a full after-action report from all parties involved" in the coming days.

The Ravens had been cruising along with a 28-6 lead in the game when, without warning, the power to the Superdome suddenly shut down early in the third quarter, plunging parts of the 38-year-old stadium into darkness and leaving TV viewers with no football and no explanation why.

For 34 minutes, the players tried to stay loose, the fans milled about in darkened corridors, and stadium officials scrambled to figure out what went wrong. The Ravens barely hung on for a 34-31 victory over the San Francisco 49ers, needing a goal-line stand in the closing minutes to preserve the championship.

Most fans seemed to take the outage in stride, even starting up the wave to pass the time.

"So we had to spend 30 minutes in the dark? That was just more time for fans to refill their drinks," said Amanda Black of Columbus, Miss.

The problem occurred shortly after Beyonce put on a halftime show that featured extravagant lighting and video effects.

A joint statement from Entergy New Orleans, which provides power to the stadium, and Superdome operator SMG shed some light on the chain of events, although they weren't sure about the source of the problem. It apparently started at the spot where Entergy feeds power into the stadium's lines.

"A piece of equipment that is designed to monitor electrical load sensed an abnormality in the system," the statement said. "Once the issue was detected, the sensing equipment operated as designed and opened a breaker, causing power to be partially cut to the Superdome in order to isolate the issue. ... Entergy and SMG will continue to investigate the root cause of the abnormality."

The FBI quickly ruled out terrorism, and the New Orleans Fire Department dismissed reports a fire might have been the cause.

On the CBS broadcast, play-by-play announcers Jim Nantz and Phil Simms went silent. Sideline reporter Steve Tasker announced to viewers a "click of the lights" as the problem. Later, the halftime crew anchored by host James Brown returned to fill the time with football analysis.

"We lost all power up here at the press box level," Nantz said after power was restored.

He and Simms were off the air for most of the outage.

The failure occurred shortly after Jacoby Jones returned the opening kickoff of the second half for a 108-yard touchdown, the longest play in Super Bowl history and pushing the Ravens to a commanding lead. But when play resumed, the momentum totally changed.

The Niners scored two straight touchdowns and nearly pulled off a game-winning drive in the closing minutes. They had first down inside the Ravens 10, but Baltimore kept them out of the end zone to preserve the victory.

The blackout, it turned out, became more of a footnote than a spark to what would have been the greatest comeback in Super Bowl history.

"It just took us longer to lose," said San Francisco linebacker Ahmad Brooks.